Automatic steering apparatus



July 28, 1953 R. J. KUTZLER EIAL AUTOMATIC STEERING APPARATUS Filed Jan. 8, 1951 SCRIMINATOR INVENTOR. ROBERT J KUTZLER DANIEL G. TAYLOR ENGAG E SWITCH l2 L IS MANUAL OPERATOR ATTORNEY,

Patented July 28, 1953 I 2,846,947 AUTOMATIC STEERING APPARATUS Robert J. Kutzler, Richfield, and Daniel G. Taylor, Minneapolis, Minn., assignors to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 8, 1951, Serial No. 204,966

9 Claims.

This invention relates to stabilizing devices of the type concerned with stabilizing an aircraft in flight. Aircraft, in many instances, have a vertical fin or stabilizer that aerodynamically provides directional stability to prevent the craft from oscillating about the yaw axis. Where the aircraft lacks a vertical fin of sufficient size or proportions to provide proper directional stability, such deficiency may be offset by operating the rudder surface whereby dynamic stability is provided.

Such operation of the rudder may be effected through a reciprocating type of hydraulic or fluid motor having a conventional slidable control valve. The valve of the hydraulic motor, during manual control of the craft, may be manually displaced. On the other hand, the valve may be displaced automatically upon the craft changing heading by an electric motor that is automatically controlled, to mechanically provide dynamic stability for the aircraft even While the valve may be also manually controlled.

The aircraft may also be supplied with an automatic pilot, to maintain the craft heading against external disturbing forces, which also has an electric motor for positioning the valve, of the hydraulic motor. The autopilot may include conventionally a compass or directional gyroscope or similar devices for automatically stabilizing the direction of flight of the aircraft.

It is an object of this invention to provide a novel relationship between a dynamic means for damping and suppressing oscillations of an aircraft, resulting from its construction, and an automatic pilot which opposes the action of external forces tending to change the craft heading from a selected heading.

It is a further object of this invention to provide a simplified dynamically operative stabilizing control for an aircraft.

A further object of this invention is to provide a dynamically operative stabilizing control that functions during manual control of flight and autopilot control of flight of an aircraft.

It is a further object of this invention to effect improved automatic dynamic stabilization of an aircraft by operating a control surface thereof under control of a device responsive to movement of said craft about an axis.

A further object of this invention is to embody in the above device a gyroscope responsive to the rate of change of heading of said craft. 7

Other objects and advantages will be apparent as the invention is more fully disclosed. The invention maybe more fully understood by referring to the following description in conjunction with the accompanying drawing which illustrates one embodiment of the invention.

The sole figure is a diagrammatic view of a heading control apparatus for an aircraft in which the present invention is utilized.

The form of the invention illustrated in the figure, by way of example, includes means for controlling a servomotor in one instance, in accordance with the rate of change of heading of the aircraft while manual operation of the servomotor is also permitted so that the rate of turn responsive device which is acted upon by the dynamic action of the aircraft effects through the servomotor an operation of a control surface to effect stability of the aircraft and correct for the inherent dynamic action of the aircraft. Alternatively, this same rate of turn responsive device is included along with a position maintaining device in apparatus to automatically maintain the attitude of the craft at a selected value, through control of the same servomotor.

Referring to the drawing, the apparatus includes a fluid operated servomotor ID for operating a rudder l l of a dirigible craft such as an aircraft. The servomotor Ill conventionally includes a cylinder l2 housing a power piston l3, which is displaceable in either direction from a midposition to operate the control surface ll. Communicating with opposed ends of cylinder l2 are conducting pipes I4, I5 extending from a control valve I1. The control valve ll comprises a valve body [8 which houses an adjustable cylindrical piston IQ of the double land type. The adjustment of control valve 19 serves to connect pressure inlet line 2| with conducting pipe [4 and connect conducting pipe 15 with exhaust line 2|].

Alternatively the adjustment of control valve I9 connects inlet pipe 2| with conducting pipe l5 and connects conducting pipe [4 with exhaust pipe 20. g

The position of control valve piston I9 is controlled by a lever-linkage arrangement 23 comprising a differential lever 24, differential lever 25, and a link 26 connecting the mid-points of the levers. One end of lever 25 is connected by a pivoted rod 21 to a piston valve I9. The oppo-,- site end of lever 25 is connected to a pivoted follow-up rod 28 additionally connected to piston 13 of the servomotor I0. One end of lever 24 has a pivoted manually operable rod 29 extending therefrom and the opposite end of lever 24 is pivotally connected to a rack 30. By means of the levers 24, 25 and link 25 the rod 21 is positioned in accordance with the resultant of three controlling quantities. The rack is positioned by a gear 32 in mesh therewith which gear is driven by an output shaft 33 extending from rotor 34 of aircraft dynamic damper induction motor 35.

The motor 35 may be a capacitor type induction motor having a line winding 36 and an amplifier energized Winding 3?. The line winding 38 is connected in series with a phasing capacitor 38 to a source of alternating voltage. The winding 37 is energized from the output of a conven, tional phase sensitive or phase discriminator amplifier 49. The amplifier 40 may be of the type as shown in the patent to Beers, 2,020,275. For simplicity it is here shown as consisting merely of two sets of triode tube. elements, The two plates are connected to the opposed; ends of a, secondary winding 43 of a transformer 4| whose primary winding 42 is connected to the source of The two cathodes are. con.-

alternating voltage. nected together and thence to ground. The two grids. are. wnnected together. A conductor 44. extends from a center tap of the secondary winding 43 to one end of motor winding 3? the opposite endof winding 3.; being connected to ground which is common with the ground or the two cathodes. The direction of rotation of rotor 34 of motor 35 depends upon which set, of tube elements are operating and this. depends upon the phase relationship between the alternating volt.- age between the grid and cathodes of the triodes andthe voltage across the primary winding, 42 of transformer 4|.

The grids and cathodes of amplifier d6. are connected to a control or first balanceable network 45 which provides control signals to effect operation of amplifier 4B. 7

Network 45 includes a'Wheatstone bridge 68 having a potentiometer 41 comprising a resistor 48 and a slider 49; a trim-potentiometer 5i comprising a resistor 52 and a slider 53; and a secondary Winding 54 of transformer 41. The transformer M of network id. is common to the transformerfor the amplifier 40 since a single primary winding of a transformer may supply a plurality of secondaries. Thus in the further networks to be described, the transformer 41 will be common to them also. Resistors 43, 52 are connected in parallel across secondary 54. A conductor 5.5 extends from the grids of the amplifier 40 to slider 49, Slider- 49 ispositionedalong resistor 43 from the mid-point thereof by output shaft 33 of dynamic damper motor 35. Slider 53 is provided with asuitable knob 56' whereby it may be manually positioned along resistor 52.

Balanceable network 45 includes a rate gyro network 58 comprising a potentiometer 5i having a. resistor 60 and a slider 6i and secondary winding 62: of transformer 41. The resistor is connected across the secondary winding 62.

Slider 6-] is positioned along resistor from the midpoint thereof by a rate of turn gyroscope. 63.

Associated with: the network 58 is an, autopilot engage relay E4. Relay E4, is of the double arm double throw type comprising anoperating coil 65 and arms 66, 61,. Each arm coacts with its individual out contact and individual in contact. Relay arm 6.1 normally engages its grounded out contact. A conductor 68 extends; from. relay arm 61: to slider 6|- A conductor 69 extends from a center tap. of a secondary winding. 62; in series with a voltage divider 10 to. slider 53 of net: work 46.

The voltage divider it! comprises a resistor 12 and an adjustable slider T3. One, end of resistor. '12 is connected. to conductor 69 and the. opposite end of resistor 12 is connected to relay arm 66. A conductor 14 extends from slider 13 to slider 53 of network 46.

The dynamic damper of oscillations of the aircraft is completed by the rate of turn gyroscope 63 which is of the conventional type having a rotor 16 rotatably supported in a gimbal ring 11 for rotation about a horizontal axis. The gimbal ring 11 in turn is supported in pedestal bearings '18, 19, the latter only partially shown, for angular movement about a horizontal axis at right angles to. the spin-.axis of the rotor it. Extending from one. of the trunnions of gimbal ring (7 is an operating connection for positioning slider 6| along resistor 69. Depending from the operating connection 80 adjacent pedestal bearing 18 is an arm 8| which is connected approximate to the mid-point ofa biasing spring 85. The ends of spring 85, are carried by arms 82, 84 extending laterally from the fixed bearing 78. The arrangement of gyroscope. 63 is such that upon movement of the craft about its. yaw or turn axis the gyroscope processes about. the trunnion supports in bearings 18 19.

An autopilot network 86 may selectively be placed in series with the damper network 45 to automatically stabilize the craft on a givenheading. Means by which such connection is effected will be subsequently described. Network 86includes a Wheatstone bridge 8? comprising a yaw attitude potentiometer 88 having a resistor 89, a slider 98; a centering or rebalancing potentiometer 9i having a resistor 92 and. a slider 83; and a secondary winding 94 of transformer 4|. Resistors 89 and 92 are connected parallel across secondary winding 94-. Slider is positioned along resistor 89 in accordance. with the magnitude of change in attitude of the craft about the turn or yaw axis which is detected by a directional gyroscope, 96.

Gyroscope 96 comprises a casing run which houses a rotor (not shown") for rotation about a horizontal axis. The casing in turn is supported by trunnions WI, [02 in an outer vertical gimbal ring 98 for rotation about an axis at right angles to the rotor spin axis. The vertical gimbal ring 98 is supported in suitable bearings. I03, 104 and movement of the outer gimbal ring 98' upon change in heading of the craft is transmitted by operating connection 105 through a directional transmission device andv operating connection S'lto slider 90.

The device si permits movement of slider 50 from gyroscope 96. during stabilization of heading but prevents such. movement during manual changes in heading through the automatic pilot and may be similar to that, disclosed in an application of Paul Shivers, Serial No. 726*,008 filed February 3, 19M, or like, the. directional arm lock disclosed in Figure 13 in. the application of Willis H. Gille, Serial No,. 447,969,, fi ed June 22-, 1942'. When the directional arm lock or the Gille application 'is utilized, the arm lock will be controlled from out contacts of a normally energized relay which is energized when stabilization from the directional, gyro 96 is utilized. The transmission device 95 when deenergized' prevents adjustment of slider 90, by yroscope 86 during selective changes in heading of the craft. Slider 93.i s positioned along resistor 92 bymotor operated means L332 whose operating means will be subsequently described.

Returning to the, network 86,, the networkadditionally includes a balanceable Wheatstone bridge BEL having a manually operable aircraft tum network 86.

control potentiometer I08 which includes a resistor I09 and a slider IIO; a vertical gyro roll attitude potentiometer III having a resistor I I2 and a slider I I3; and a secondary winding I I4 of transformer 4I. Resistors I09 and I I2 are connected in parallel across the secondary winding II4. A conductor II5 extends from slider IIO to slider 93 of potentiometer 9|. A ground conductor II6 extends from slider II3. Slider H0 is positioned along resistor I09 from the midpoint thereof by a manually operable turn control knob II1. Slider H3 is positioned along resistor II2 from the midpoint thereof by a vertical gyroscope I upon movement of the craft about its roll axis.

Vertical gyroscope I20 is of the conventional type having its rotor not shown supported in a casing I2I for rotation about a vertical spin axis. The casing I2I is supported by trunnions I22, I23 in an outer gimbal ring I24 which is cross trunnioned about axis I25 in pedestal bearings I26, I21. Upon movement of the craft about the roll axis .gimbal I24 'tilts about the aXis I25 which tilt is communicated to slider II 3 to position slider I I3 along resistor I I2.

Any unbalance in network 86 results in a voltage appearing between slider 90 and slider II3. This resultant voltage, during operation of servomotor I0 from the manual operator 29, results in arepositioning of slider 93 to balance the second The operation of slider 93 is provided by the following means. Slider 93 is positioned by a suitable operating connection I32 extending from a reversible direct current rebalancing motor I33. The motor I33 may be provided with a permanent magnet field derived from permanent magnets I34, 135. The motor I33 includes an armature I36 having one brush connected to a conductor I31 and the other brush connected to a conductor I38. Across the conductors I31 and I38 is a resistor I39 having a center tap connected by conductor I40 to ground. The conductors I31 and I38 are connected to a source of direct voltage through relays alternatively operated by an amplifier I4 I.

The amplifier MI is of the phase sensitive or the phase discriminator type having alternating voltage input connections I42, I 43 connected to the source of voltage and alternating voltage signal input connections I44, I45 connected to a source of control signal voltage. One or the other of the relays'in amplifier I4I are energized depending upon the phase relationship of the control signal across connections I44, I 45 with respect to the alternating voltage across the supply connections I42, I43. The amplifier may be such as disclosed in the patent to Gille et al. 2,425,733 or Hamby 2,466,702 wherein in the latter conductor 220 and conductor 222 are connected to the D. C. supply voltage source and conductors 224 and 226 correspond with conductors I31 and I36 herein. I

The application of a control signal to amplifier MI is controlled by a'relay I46. Relay I46 has an operating coil I41 and a single arm I48 normally engaged with an out contact I49. A conductor I50 extends from relay arm I48 to input connection I44. The other input connection I45 is connected to ground. A conductor I5I extends from conductor I30 which is connected to slider 90 to out contact I49 of relay I46. It is thus apparent that with the relay coil I41 unenergized a resulting signal in network 86 due to unbalance thereof is applied to amplifier I4I. Amplifier I4I effects closing of one or the other of its relays to effect rotation of network rebalancing motor I33. Motor I33 in turn through its operating means I32 positions slider 93 to efiect rebalance of second network 86.

In order to effect a combination of networks 45 and 86, there is provided in parallel with conductor I5I a conductor I52 which extends from conductor I30 to out contact I53 of relay arm 66 and in contact I54 of relay arm 61.

The operating coil 65 of relay 64 and the operating coil I41 of relay I46 have their energization controlled by a single pole single throw switch I55 which is placed between them and a source of direct voltage such as battery I 56. In series with the single pole double throw switch I55 and effective to control energization of the transmission means 95 is a directional gyro locking switch I51. This switch I51 includes a fixed contact I58 and a pivoted contact I59. Contact I59 is carried at one end of lever I60 pivoted intermediate its ends. The opposite end of lever I60 has a lateral extending portion I6| which engages a notch I62 in a disc I63. Disc I63 is carried on the spindle I64 of turn control knob I I 1. It is apparent that upon rotation of knob I I1 in either direction the cam I63 is rotated so that the portion I6! rides up out of the notch I62 to thereby rotate lever I60 in a clockwise direction to separate the contacts I58, I 59. The separation of these contacts breaks the energizing circuit to transmission means 95 to disable gyroscope 96 from operating slider 90.

Use is made of the rate of turn gyroscope 93 as a control device in two configurations for controlling the hydraulic servomotor I0. In one configuration the pilot adjusts directly the manual operator 29 to operate servomotor I0 to control the position of rudder II. In the other configuration, the aircraft is stabilized on a select heading by means of the directional gyroscope 96.

During manual flight, the engage switch I55 is in its unoperated position as shown. At this time the operating coils and I41 of relay 64 and I46 are unenergized. Also the transmission means 95 has its circuit broken so that the directional gyro operated slider may be returned to its center position as the arrangement of the aforesaid Shivers application or may be held against further movement from directional gyroscope 96 as in the aforesaid Gille application.

If the aircraft tends to change heading, such change in heading is reflected in the precession of the rate of turn gyroscope 63 depending upon the rate of change of heading. This precession of gyro 63 adjusts slider 6| to change its potential with respect to the center tap of secondary winding 62. Slider BI is connected through conductor 66, relay arm 61 to ground and thence to the ground of the cathodes of dynamic damper amplifier 40. The center tap of secondary winding 62 is connected by conductor 69 and voltage divider resistance 12, conductor 14, network 46, conductor 55, to the grids of amplifier 40 whereby a control signal is applied to the amplifier. The amplifier 46 effects energization of the motor winding 31 to set up a rotating field whereby rotor 34 is rotated. The rotor 34 displaces the slider 49 whereby a voltage is derived between slider 49 and slider 53 equal and opposite to the voltage between slider 6i and the center tap of secondary winding 62 to balance network 45. The rotor 34 additionally through the the piston I3 of servomotor In to position rudder II. Simultaneously the movement of pistion I3 through the follow ip connection 28 recenters the valve F9. The displacement of rudder It is therefore in accordance with the rate of change of heading of the craft: and serves. to check the inherent tendency of the aircraft: to yaw and thus provides dynamic stabilization.

During the above stabilization operation, any unbalance of the second network 85 results in a diiierence of potential between slider 8-0 and slider H3. slider 99'- is connectedthrough conductor I30, conductor I51, out-contact I49, relay arm M8, conductor i 50, to input connection N4 of amplifier- I 4 I'-. Conductor H3 is connected through conductor M6 to ground which is common to the ground connection I45 of amplifier MI. The amplifier I-4I efiects operation of motor I33 which positions slider 93 to rebalance the second network 8'6.

Should the pilot desire to change heading di rectly, he positions operator 29- to effect operation of the hydraulic motor It. It will be evident that the rate of turn gyroscope 63 opposes this manually induced change of heading and its adjustment of slider Si is followed automatically by motor 35 moving slider 49. Cons quently the pilot must displace the operable rod 29- an additional amount in order to compensate for the movement of the rack 35 induced by precession of rate gyroscope 63. Upon cessation of turning, the spring 85 tends to return the preeessed gyro rotor it to its normal position, thereby returning slider iii to the center of resistor 66. The first network 45 is reversely unbalanced due to slider 43- being displaced and motor rotates in the opposite direction to return slider 19 and rack 30 to their normal positions.

With the manual operator having been positioned to select a new heading, it may be desirable to automatically maintain the craft onthis heading. Automatic heading control is introduced by operating engage switch I55. Closing of switch I55 energizes as stated the operating cells 65 and Id? of relays 64 and I43. Additionally closing switch I55 extends this energizing circuit which includes switch I55, conductor I61, switch I'I=, conductor I58, transmission device 95, to ground and to ground of battery I56.

Operation of relay coil 65 in efiect places the variable resistor I6 across the slider tI of potentiometer 59 and the center tap of secondary winding 82 as a voltage divider, and additionally connects sl-ider- BI by means of conductor 68, relayarm 8?, iii-contact I54, conductor #52, and conductor I to slider 9B- of potentiometer 88. Thus relay 85 serves additionally to connect the first network 45 and the second network 88- in series relationship whereby they jointly control the dynamic damper amplifier 4!]. The operation of relay I46 breaks the input circuit for. controlling amplifier HI thus motor I33 becomes disabled from operating slider 93.

Should the aircraft due to an external transient disturbance change its heading, such change in heading is detected by the directional gyroscope 96 which through transmission means 95 effects operation of slider 9B. Additionally therate of turn gyroscope 83 responds to the rate of turn of the craft and positions slider SI along resistor 68'. The amplifier 45 operates in response to the displacement and rate of displacement signals and effects rotation of motor to operate slider 49 to rebalanee the joint or series connected networks. Additionally the. motor 35 operates through the pinion 32 and rack. to transmission arrangement 23 to controt valve to of servomotor I0 to: displace the rudder It.

When the craft has reached its maximum deviatio-n from the selected heading and returns to- Ward a normal position, the rate of turn of the aircraft is in an opposite direction from that formerly encountered due to the disturbance, andtherefore the slider GI ismoved in an opposite direction to derive a signal which opposes the displacement signal from slider 80. While the decreasing displacement signal from slider would tend to move the rudder back to its normal position, the opposite signal from slider GI due to precession of gyroscope 63 tends to accelerate this returnof the control surface to its normal position. Thus as the craft in its recovery from the deviation nearly regains its original position, the signal from the rate gyroscope 93 may be of such value as to induce an opposite displacement of the rudder I I- thereby to check any tendency of the craft to move beyond the selected heading.

If desired, the heading of the craft may be selectively altered through the automatic pilot by operating the turn control slider I-I'il'. Operation of slider i'lfl' rotates the disc I53 to break the circuit to transmission device 95. The gyroscope 86 is thus disabled from operating slider 98', and the signal from the displacement of slider I it-unbalances the series connected net.- works G5 to effect through amplifier 4t and motor the operation of the valve I! of hydraulic. servomotor I0 and a resulting rudder movement to change craft heading The gyroscope $33 opposes this change of heading and modifies the amount of rudder displacement originally obtained from the displacement of slider lI'il manually. When the desired heading is approached, the slider III] is manually repositioned, and the rate of turn gyroscope 63 pro- Vides an opposite rudder displacement which prevents the craft from going beyond the selected heading.

It will. now be apparent that there has been provided. means for stabilizingv an aircraft by displacing a control surface thereoi which means is responsive to the dynamic movements of said aircraft about the axis tov be controlled due to the inherent instability of said craft about saidaxis. Further that. such arrangement functions when the craft is being directly manually controlled, when no automatic stabilization to offset inherent instability would otherwise be. provided, and also when it is being controlled through an automatic pilot to effect a damping action to impede movements of the craft from a selected heading. While one embodiment of the invention has been disclosed, it is to be understood that such is for illustrative purposes only.

What. is claimed is: V

1. Control apparatus for a diri'gible craft having a control surface, said apparatus comprising: servo means for operating said surface; an elecmotorfor controlling said servo means; means responsive to rate of turn of said craft for operating said motor; meansresponsive to change in headingforproducing a first voltage, a rebalancing motor; means driven by said rebalancing motor for supplying a second voltage: a control means for said rebalancing motorresponsive to a difference of said first and second voltages; and selective means for rendering said 9 first and second voltages ineffective on said control means and additionally controlling said electric motor from said first or heading change responsive means voltage and said second or rebalancing motor voltage. V

2. Control apparatus for an aircraft having a rudder, said apparatus comprising: a hydraulic servomotor having a control valve for operating said valve; manually operable means for directly actuating said linkage for controlling said motor to change craft heading; an electric motor having a movable member operatively connected to said linkage for additionally controlling said servomotor; means responsive to rate of change of heading for generating a signal; signal operated means controlled by said signal for effecting operation of said electric motor; a craft heading change device for generating a signal; means for preventing said craft heading responsive device from generating a signal during manual changes in course; and means for additionally controlling said signal operated means from said heading change device to maintain the craft on the manually selected heading.

3. Control apparatus for operating a control surface of an aircraft comprising: a hydraulic servomotor for operating said surface; means responsive to rate of turn of said aircraft about an axis; an electric motor for controlling said servomotor; signal responsive means for controlling said electric motor; a balanceable network for operating said signal responsive means on unbalance thereof; a signal generator operated by said rate responsive means; a rebalance signal generator operated by said electric motor; both of said generators being included in said network; a second balanceable network; position maintaining means responsive to movement of said craft about said axis; a network rebalancing motor; a second signal responsive means for operating said rebalancing motor; a pair of signal generators in said second network, one being operated by said position maintaining means, the other by said rebalancing motor; manual means for controlling said hydraulic servo to change the position of said craft about said axis with said control modified by said rate of turn means; and means for connecting said second network to said second signal responsive means during such manually controlled change in position.

4. The apparatus as set forth in claim 3, with means for rendering said positioning means ineffective to operate its signal generator during manually controlled changes in heading.

5. The apparatus of claim 3, with means for connecting said two networks in series relation, and rendering said second signal responsive means inoperative during said connection.

6. In control apparatus for an aircraft having a motor means for operating the rudder of said craft, and a mechanical differential device for controlling the motor means: manually operable means operatively connected to one part of said device for controlling said motor means; mechanism connected to another part of said device for selectively controlling said motor means; said mechanism including attitude reference means responsive to variations in attitude of said craft, rate of attitude change responsive means, servo means controlled by said attitude reference means and said rate of attitude change responsive means for maintaining said craft in a selected attitude; means in said mechanism for varying the attitude at which said attitude refid erence means and servo means maintain said craft; and means for disabling said attitude reference means from controlling craft attitude during control of said differential device for said motor means by said manually operable means and controlling said servo means from saidrate of attitude change responsive means.

7. In control apparatus for an aircraft having a control surface for positioning said craft about an axis and having a hydraulic motor means for operating said surface, with a mechanical dif-' ferential device for positioning a control valve for the hydraulic motor means said apparatus comprising manual means for controlling said motor means; in combination, a balanceable network having a signal generator operated on change in position of said craft about said axis and a network rebalancing signal generator; a first control means selectively responsive to both said signals for actuating said rebalancing signal generator; a second balanceaole network having a signal generator operated in accordance with the rate of change in position about said axis and a second network rebalancing signal generator; a second control means responsive to unbalance of said second network for operating said second network rebalancing generator and operatively connected to said diiferential for concurrently controlling said motor means; and means for connecting said networks in series relation and rendering said first control means ineffective to actuate said rebalancing signal generator, to maintain a selected position of said craft about said axis.

8. Apparatus for controlling the heading of an aircraft having a motor means for operating a rudder control surface of said craft which motor means has a mechanical differentially operable control device that may be directly manually operated from the control column of the craft, power apparatus for also operatin said control device, said power apparatus comprising: signal responsive servo means operatively connected to said control device for additionally controlling said control surface motor means; heading responsive means for generating a signal in accordance with the magnitude and direction of change in heading; manual means for producing a heading selection signal; a balanceable signal combining network for operating said signal responsive servo means; means responsive to the rate of change of craft heading for generating a rate signal; a follow-up signal generator operated by said signal responsive servo means; means for selectively controlling said signal responsive servo means solely from said rate responsive means signal and said follow-up signal; and means for maintaining said heading responsive signal generator ineffective and for equally opposing said manual heading signal during such selective control of said signal responsive servo means.

9. In control apparatus for an aircraft having a control surface power means said power means having a controller that may be directly manually operated, means for selectively controlling the heading of said craft in accordance with a plurality of signals comprising a heading responsive device for supplying a first voltage signal varying with heading of the craft; means for producing a second variable voltage signal; a motor means controlled by said first and second voltage signals; driving connections from said motor means to said second variable voltage producing means and to said controller for said power means; means for rendering said heading responsive device ineffective to produce a voltage during manual operation of said controller; means responsive to rate of turn of said craft for producing a third variable voltage signal; and means for automatically applying a portion of said rate voltage to said motor means w-hile said heading responsive device generates asignal voltage and for applying the full rate voltage signal to said motor means while said heading responsive device is made ineffective to generate a voltage signal.

ROBERT J. KUTZLER.

DANIEL G. TAYLOR.

References Cited in the file of this patent UNITED STATES PATENTS Number 

